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Svenson Prima, 3-Axis Trainer, from a Svenson kit...

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    #16
    The trimming of the upper fuselage sheeting was easy enough...



    ... and what it looks like, right side up...



    It's getting closer and closer to the appearance of a 'plane, rather than pieces of balsa stuck together, no..? Still, I'll be needing those magnets to arrive to be able to advance much more.
    Turning back, then, to the wing... The inner ribs had to wait for the wing joining, so as to be fitted either side of the dihedral key. I knew this was to be fiddly, and I was not wrong. I would have preferred these half-ribs to have been die-cut at the factory. Still, it has to be done, so I measure them up and cut 'em. The root rib of the covered wing goes in, then the first one of the exposed wing. This half-wing is still in a fragile state, and to match things up, a little strapping is required...



    I've only done one (of three...), as there is little support to be had. All will be consolidated when the sheeting goes on; until then, I prefer to patiently do as much as seems solid and stable enough, then leave it to set. That's all for this evening, then. I should be able to finish off these half-ribs tomorrow, but will probably leave them alone to really get some strength, and continue the fore top sheeting the next day. We'll see...

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      #17
      Not much to report today, but a big step, just the same. The last of the ribs are now in place...



      As suspected, it's too cold for the glue to set in a reasonable time, so I'll leave it all until tomorrow now, as there is still no sign of the long-awaited magnets for advancing the fuselage hatches.
      Tomorrow, the top sheeting goes on, probably.

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        #18
        I went to check on the state of my wing, and found that the ribs have nicely set, faster than I had thought. It only took a few minutes, then, to adjust a fresh sheet to the top fore of the half-wing remaining, and glue it to the leading edge...



        Here's another view, looking through the structure to the inside, where the tips of the clamps are just about visible...



        That, now, will take the time it needs to set (tomorrow afternoon or evening, maybe..?) before gluing it down over the ribs and spar. Progress..!

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          #19
          The leading edge is set, so the sheet is bent over the ribs and taped down...



          Yes, of course, more pressure is needed than simply tape, so out come the books again (making sure that the half-wing is held down really flat to the building board...)...



          Later on the same day, once the PVA has set, the tape comes off, and the upper trailing edge strip is glued and clamped...



          It's feasable to finish off the top sheeting at the same time; it's cut to size, glued and taped...



          A bit of help from the library won't go amiss; it's worked well enough so far...



          Dumb question: is this what's known as 'book-binding'..?
          Tomorrow, the last of the under-wing sheeting...

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            #20
            This is how the top sheeting has turned out...



            ... and a closer look at the centre section...



            There are a couple of spots that will need a bit of sanding or trimming, but, in general, I'm pleased enough with the way it's gone so far. There are still the rib caps to apply, though, so here's the start of that...



            ... and the result, all glued up and taped...



            I'll spare you the photo of the 'book-binding' (although I took one, of course..!).
            Once that's all set, it'll be the last leg for the wing structure, with the curling over of the lower front sheeting. Maybe this evening; probably tomorrow...

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              #21
              The first sheet laid down on the plan was the under-sheet; it's now the last sheet to be glued up. The same tiny glue pot and a fine paintbrush for application, then binding, to hold it until the PVA goes off...



              Some time later, here's the result...



              A bit of checking for planity; all seems correct; good..!
              Who can resist, once the wing is complete, trying it out on the fuselage..? I certainly can't..! The tailplane and fin are merely put in place for the photo, of course...



              It's encouraging, but there's still more to be done, nonetheless. The wingtips need finishing. I'd already started one, but left it for other tasks; now's the time to get it done. Of all the work done so far, I think that this is the least agreeable. I try all ways to get the supplied piece to fit, but, in the end, and in desperation, I use it as a template and cut another from stock sheet, over-size. That's much better, but still an awkward shape to fit..! I should have done that from the start, rather than struggle. I finally decide that it'll just have to be glued up and take its chance. It gets trussed up like a chicken to hold it in place...



              Not the most elegant, I'll admit, but pins were on no use; I've no idea how that could be done with magnets. I see the advantages of carving solid tips from block balsa, or foam. I didn't have this trouble with the Electra, as the tips are not sheeted, but filmed. Too late to take that option here, but it's tempting..!
              Enough whinging; there's another needs starting...



              Only that one gusset in place for now; I'll leave that to set and get the washing-up done. Back later...

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                #22
                The photo before last shows us the 'trussed-up chicken' wing tip. Well, the following year (Happy New Year..!), this is the result, raw, before trimming...





                Not spectacular, but at least the glue and binding have done their job; it's held up quite solidly. I'll be able to trim and sand it, but first, I prepare the other 'chicken' for later on...



                Yes, I know; it looks awful. The important thing, though, is that it maintains the glued edges and surfaces tightly together, without twisting or straining anything. We'll leave that, then, and get on with tidying up the first one.
                Roughly half an hour later, the 'rough diamond' of a wing tip is turned, if not into a precious gem, at least into a semblance of neatness..!





                That'll do for now. The whole wing will need a good rub down, and maybe a spot of filler here or there, so I'll let the last tip go off, give it the same treatment, maybe this evening or tomorrow, and start to prepare for covering (mentally, at least...).
                To be continued...

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                  #23
                  We left the second wing-tip all bundled up; this is what came out of the bundle...





                  A bit rough around the edges, but all stuck down, which is a Good Thing. A bit of sanding; still needs a final touch of gloss, but it's a bit tidier...



                  When joining the wings, there was a bit of a bulge on the underside at the joint, due to a slightly misplaced root rib. It could have passed muster, but I decided that I'd rather try to fix it, by cutting away the offending part of the panel, trimming the rib and putting in a couple of supports...



                  ...the panel was then glued back in place and taped up...



                  ... which eliminated the bulge, at the price of a few scars...



                  Once buffed down, maybe a spot of filler, it'll be acceptable. Not my finest moment, but the bulge pleased me even less.
                  On, then, to the next stage, which involves gluing on the fixed part of the trailing edge at the wing centre, where the wing retaining bolts will go. The pieces were pre-formed, part of the kit, and are simply glued on. I have to be confident that the glue will be stronger than the wood, and that this simple butt-joint is sufficient to take the strain. It'll be helped by the fibreglass tape I'll be using around this joint, so I'm happy enough; after all, this is a trainer, not a 3D acrobatic 'plane..! Yet another method of 'clamping' is used...



                  There are a pair of ply reinforcement plates to glue on now, trying to foresee the alignment with the wing bolts...



                  Some careful measurement and marking, before gluing and clamping the ply...



                  The test will come when the holes are drilled, but I'm pretty sure we're not far off. Any smart tricks for finding the exact spot to drill..? I might be able to find a couple of steel bolts with this thread, and convert them to marker points. I'll have a scout round and see.
                  That's enough for this evening, though...

                  Comment


                    #24
                    There's one last piece for the fuselage: a cross-piece to support the trailing edge over the cabin, where the wing bolts will be holding the wing down. The plan calls for a simple piece of square; I've cut a slightly 'beefier' piece to marry exactly with the angle of the trailing edge, to ensure full support and stability, and glued it into place. Careful examination will reveal the 6mm bolts I'm going to use to find the exact spot for drilling the wing bolt holes. I'll edge them up, little by little, until they leave a mark on the underside of the wing; that'll be where to drill (I hope..!)...



                    Once again, a method has to be found to hold the piece in place as the glue goes off; a steel rule is pliable enough, and, hopefully, will spring back to 'straight' afterwards..!

                    A few details now need sorting. One such is a weakness at the nose, where the 'chin' sheet has a split. I thought that the best remedy would be a 1mm ply patch inside, glued flat after having 'wicked' PVA into the split. It's clamped down firmly...



                    I know of no better way of making long-awaited parts arrive than to do without them..! With that in mind, I've decided to change the hatches over the motor and battery compartment, by uniting them into one, and changing the orientation so as to feed the new hatch from the front. To this end, I'll need to reverse the current peg for the battery hatch, taking it to the other side of the firewall, and attaching it to the underside of the new, longer, hatch. I can use the same piece, line it up with the dowel hole, then glue the hatch onto it. This should ensure alignment. This is the peg and its support; the blue masking tape is to ensure that the hatch doesn't stick to the firewall if there's any glue creep...



                    Here are the constituent parts of the new hatch system. The two present hatches (to the right of the fuselage...) will be put in place on the nose, then a ply sheet (to the right of the two hatches...) laid over, to join them together...



                    Here, the complete assembly has been presented over the nose, with the dowel peg in place. The new hatch has to be firmly held down to glue the peg support to the hatch, from underneath. Our trusty hammer does the trick, as usual...



                    Slight complication: the nose has a top curve, so 'persuasion' is needed to hold the ply sheet flat to the motor hatch. The hammer of course, but not only...



                    Whilst all that is drying, I can go over the whole wing, using balsa filler and sandpaper to get a decent finish in preparation for covering. 'Twon't be long now...



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                      #25
                      Short, but sweet...

                      Now that the wing bolt supports are all in place, there's no point in putting it off any longer. The bolt holes are to be drilled in the fixed part of the trailing edge. How to align the holes with the threaded holders beneath, blind..? Thanks to a buddy for the tip: cheese-head bolts are screwed in, leaving the heads just flush with the underside of the wing when it's in its place. I start with the bolts slightly lower, then raise them a bit at a time until I feel that they touch the wing. Some blue marker is then applied to the heads and I offer up the wing again. Bingo..! There is enough of a round mark to be able to determine the centre of the future hole...



                      The suspense is not yet over, however. The threaded holders are installed (as per the plan...) at an angle, so the bolt holes, too, have to respect that angle. I mark an approximation, by eye, on the trailing edge, then go for it..! A 3mm pilot hole, then a 6mm. The bolts are 6mm, so I pass a 6.5mm through, and here's the result...



                      The two bolts slide through, with no 'play', and meet up with the threaded holder below. Pleased..? Yes, I'm pleased; I apprehended this stage, as it holds great scope for messing things up, and I really didn't want to have to patch up a bodged job. Thanks again, then, that hint worked a treat.
                      I've not screwed the bolts fully down yet, as they're a bit tight, and will benefit from a touch of lubrication. Still, an important step has, again, been taken..!
                      Next thing will be the marking out, cutting and dry fitting of the hinges for the control surfaces. Maybe later this evening; maybe tomorrow. Again, care is needed, so I'll go easy, and not rush it.
                      To be continued...

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                        #26
                        With the new hatch cover in place, I was not happy with the fit over the motor bay; the ply needed to bend more. Not wanting to make another hatch altogether, I decided rather to fill the gap, thus reducing the curve required. Using offcuts (I throw little away..!), I could lay them over the motor bay flanks, but needed to sand them down with a taper. How to ensure I don't sand too much..? A variant of a tip seen on other build logs: a couple of wood screws were taped to the nose, preventing the sanding block from rubbing further down at that end...



                        The result..? A much better fit...



                        ...which enables me to carry on sanding the fuselage, rounding off the corners and edges...



                        The fuselage can now be put to one side, ready for covering. Now for another 'fun' task which I'm not looking forward to. Hinge slotting. Hands up those that revel in this activity..? No, I thought not; not many huh..? I'm not surprised. In a previous post, I described how I'd gone about slotting the hinges for the elevator. I 'invented' a tool for the job, but was not convinced that it was the best that could be done. Having seen positive revues on the subject, I invested in a Dubro slotting kit. 'At last..!' thought I, 'A tool which will make this much easier.' Well, not entirely wrong, but not entirely convinced, either. After a few trials on scrap pieces, I launch into the slotting for the rudder. I start by marking the hinge locations, after taping the pieces together to ensure a match...



                        Then comes the gruelling part. Plunging the cutter into the delicate assemblies that I've been carefully protecting all this time..! Another mistake was revealed, too. It was not a Good Idea to profile the leading edges of the rudder. It makes finding the centre line with the parallelogram tool quite arbitrary..! Still, needs must, so I plunge away...



                        Hmm... Not too bad, but not much easier than my makeshift tool. The centering gadget is worthwhile, though.
                        On to the ailerons, then, where it's a very different story. If the ailerons themselves get slotted with reasonable accuracy and ease, not so the wings..! Behind the trailing edge is a balsa reinforcing block, placed there on the plan exactly for giving enough meat for the hinges. All well and good, but the balsa used is of a very different category; very hard and resistant. The poor slotting tool bent and twisted, and it started to feel more like butchery than model-making. Another approach was required...
                        Dremel to the rescue. I improvise a jig, raising the wing on a couple of stock sheets (if ever one wonders why it's a Good Thing to buy those cheap bundles of balsa, here's one of their many uses...). The Dremel, in its holder became the right height to be able to chain-drill the slots, using a 1mm bit...



                        I could slide the Dremel across the table and maintain the orientation quite easily. Once the drill bit had done most of the 'heavy lifting', it was much easier to finish off with the Dubro tools, and the final result was much cleaner. Lesson learned; next slotting session I'll go straight to the Dremel solution, I think.

                        Once again, the time is ripe to put all this stuff together, to see how it will turn out. Here, then, is the progress so far...







                        Still only naked wood, of course, but no longer a bunch of sticks and planks..!
                        What's left to do..? I'll take delivery of laminating epoxy tomorrow or the next day, which will be for the glass fibre tape around the wing joint. I've just enough left from the Electra kit; I'll need some more for my next builds.
                        Whilst mounted in this 'raw' fashion, I loaded her up with all the gubbins (a technical term...) to see if the C of G was somewhere close, and help with deciding battery location. At first, with the battery I'd intended to use, the 'plane wouldn't even stay on its nose-wheel..! Two batteries did the trick, and a rough test of CoG seemed to be perfect. I weighed the whole 'plane, too; she turns the scales, fully loaded but naked, at just under 1200 gr. I don't know if that's great or poor, but it's too late to change much, anyway..! I weighed the 3s Lipos at 110 gr each, then tried a 4s, much heftier, at 315 gr. Although it's rated for 4s if required, I think I prefer to start off with 3s, as I'm not looking for performance and acrobatics; rather a staid, stable flight for a beginner. I'll look, then, for a 3s weighing around 300gr.
                        Phew..! A long post, eh..? Next up..? Probably the covering, after the taping of the wing joint. That's all until then, then...

                        Comment


                          #27
                          It never fails...

                          I mention in a couple of previous posts in this topic my order for magnets, placed in the first days of December. These were to hold down the hatch over the motor, but were long in arriving. I decided a few days ago to go without, and remodelled the hatch so as to no longer use these ordered magnets. Yes, you've guessed correctly; they arrived in the post this morning..! D'oh..! They'll be useful for future 'planes, of course, but still... I ordered tiny ones, but was still surprised when opening the envelope; they really are tiny..! Luckily I ordered a hundred, as only one would be almost invisible. I'll try them out later on, to see just how powerful they are. For the moment, despite their size (or lack of it...) I couldn't separate just one. I'll try later sliding 'em apart, but for now they're well and truly locked together. Still, that bodes well for their intended usage.

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                            #28
                            Now that the hinges have been measured up and prepared, the leading edge of the ailerons can be chamfered. They need to be held steady, and preferable at an angle, so I put one on top of the other, and pass pins through both into the building board. Not quite a 45°, but a decent head-start. I'm using a small block plane for this (some call 'em 'finger' planes, I believe...) and go steady, keeping the sole at a slight angle to get the final chamfer close to 45°. I've marked a centre line along the aileron, so as to see how far I've got. Here's the first shavings...



                            ...and, a pile of shaving later, the result...



                            A rub down with sandpaper to smooth 'em off, and they're done.
                            One last task, then, before covering: the fibreglass ribbon for the wing. The epoxy was delivered this morning, so I got that done this evening. No photos of the process, as I was a bit busy sorting out stuff, and there's not too much time to waste. An example..? I 'borrowed' the digital kitchen scales so as to get the exact proportions by weight. A container on the scales, reset to zero, and I start to pour in the epoxy. The scales don't register. Zero grammes. I pour a bit more, and more yet; still no reading. The scales decide then to 'time out', and the screen goes blank. Darn it..! How much is in the pot..? Dunno. I quickly get another, identical, pot (a glass yoghurt jar...) and weigh it. The scales oblige, so I weigh the jar with the epoxy. 20 grammes..! Far too much for the task in hand, but at least I now have a reference weight for the hardener, needing a ratio of 1 to 0.6 by weight. OK, then, I have to add 12 grammes. I zero the scales, take the hardener, and pour it in carefully. The scales don't budge. I pour in a bit more. Still nothing. Again, thinking that the measuring is over, the scales shut down. I'm left finishing off the pouring to 'guestimate' a ratio of 1 to 0.7 by volume. How close did I get..? I'll know when (or if..?) the epoxy 'goes off'. Thirty minutes at 20°C, but it's much colder than that in my workroom, probably closer to 7 or 8.
                            I'd already prepared the tape, marking and cutting slots for the dowel pegs, and striping each side of the area to be 'glassed' with a band of masking tape. I've given a small brush a severe trim, too, as I'll be more 'stippling' than painting with it. Not the easiest of jobs, but I think (I hope..!) I got away with it; here's the final result, after removing the masking tape...



                            I'll know tomorrow if the epoxy has gone off correctly or not. Fingers and toes crossed until then...

                            Comment


                              #29
                              Part I of the covering...

                              The reinforcing ribbon has gone off very nicely, so, after a final rub down, I'm ready to start covering with film. I've not done this for quite some time, so I prepare the workspace, and start off with the small elements which, in theory at least, will pose less problems. First up are the servo trays...



                              The only slight trap here is that these are ply, not balsa, but they are a decent enough 'starter' for me. The elevator is next, and cooperates nicely...



                              On, then to the other bits and pieces in white: the ailerons, motor hatch and tail-fin; I change colour for the tailplane and rudder...



                              Now that I'm feeling a bit more confident, it's the turn of the fuselage. It's to be done in two colours: 'burnt orange' (it's really yellow, though...) for the front...



                              ... and white for the rest. No great pitfalls; I'm glad that you can't see the slight wrinkles in places, though..!...



                              Now up to full speed (although I'm slow, really; it's just an expression...), we start the underside wing panels. Orange (OK, yellow...) for the ribbed spaces; white for the sheeted parts. I enlist our eldest to help trim the edges, as I can't hold the wing and the knife at the same time...



                              All goes off quite smoothly; I'll not tension these panels until the top is done, though. I turn the wing over and start to cover over the ribs again. Oh no..! Catastrophe..! I suddenly find the true cost of 'chinacote'. After tacking down the film, I start to go around the edges. A whole corner, at the wing centre section, has no glue..! It'll shrivel up well enough, but sticks to nothing..! Darn it..! Luckily, it's not so well stuck down that I can't strip it off, with the aid of the iron...



                              I see no sense in trying another piece of film; the faulty piece was from the cut edge of the roll, so I would guess that the next part of the roll will also have no glue. How much more of the roll, indeed..? No, I'll leave the wing for now, and find another source of film. I doubt that I'll be buying much more of the cheaper stuff (hap'eth of tar, and all that...). That's all, then, until the postman brings a fresh batch of orange. It may even turn out to be really orange, and not yellow..!
                              To be continued...

                              Comment


                                #30
                                Whilst waiting for the new film to arrive, I can install the hinges on the control surfaces that are already covered. Once again, I prepare the space, and start with the rudder, then the elevator, and finally the ailerons. In order to pierce the film at the correct location, I line the piece up with its counterpart, tape 'em lightly together with a spot of masking tape, then put a couple of dots on the edge to be slit. That's one advantage of using translucent film; I can see where the slots are, and, as I've chosen to have one white, the other translucent for all the hinge lines, I can rely on not accidentally covering both sets of slots, leaving no easy way to find 'em again.
                                When it came to the turn of the wing, I used the same method of alignment. As I removed the masking tape, after having marked the ailerons, to my astonishment, the orange (yes, I know; yellow..!) film came away with the tape..! It took no effort at all to peel away all the film from both wing panels I'd done yesterday..! So much for the glue, then. I'll consider myself lucky to have discovered this now, rather than in flight. The fuselage has also this yellow film on it, but as it's planked, and not open structure, maybe the film will stay on a bit better. I'll test a small part, but I'd rather not risk removing it all from there if it's not absolutely necessary.
                                So now the wing is back to its natural wood, and will be covered entirely with the new Oracover (and the white I already have...).
                                The hinges..? Yes, I did get them done, but no photos of the work in progress, as I'd left the camera by the PC, and had already mixed up the epoxy. Not too much time for doing all the parts; no rush, but no time to waste, either. I used a toothpick to get a little epoxy into the slot (not very easy...), then offer up the hinge, which has four little holes in each section. With the toothpick I fill those holes as best I can, then slide the hinge into position. Just before it reaches the full depth, I wipe away any excess from the hinge line, then achieve the positioning, making sure that it's lined up square and able to flex in both directions. Altogether, about two hours for the whole operation; the glue was just starting to stiffen up when I was finishing the last one. Here they all are, on display...



                                I'll be able to fit them to their respective parts, but I'll wait until the wing is ready, then do them all at once, so as to not have to mix up this messy stuff more than I need to. I ended up holding the pieces with tissue paper so as not to leave glue marks on the film. I find it difficult to work with this stuff and keep my clumsy fingers completely free of it.
                                This evening I may be inspired to finish off the servo trays, but it's far from certain, as I'm not feeling well. Tomorrow, maybe...

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